Pressure biased power take off valve

ABSTRACT

A pressure control valve for a power take-off clutch and brake which is pressure biased to a clutch operating position when the valve is initially positioned in the clutch operating position.

United States Patent m1 [111 3,722,542

Matthews et al. Mar. 27, 1973 [54] PRESSURE BIASED POWER TAKE-OFF VALVE[56] References Cited [75] Inventors: Ralph W. Matthews, New Berlin; 7UNITED STATES PATENTS Nicholas W. Semeniak Milwaukee, both of wis-2,945,481 7/1960 Carls ..137/596.1

[73] Assignee: Allis Chalmers Corporation, Mil- Primary Examiner-l-lenryT. Klinksiek waukee, w Attorney--Arthur L. Nelson et al.

[ pp 201,292 A pressure control valve for a power take-off clutch andbrake which is pressure biased to a clutch operat- 52 US. Cl ..l37/596.l2 222: 51 int. Cl ..F16k 11/10 p g p [58] Field of Search ..l37/596.1,596.2 10 Claims, 3 Drawing Figures PATENTEUHARZTIBYS ail.

h mwww PRESSURE BIASED POWER TAKE-OFF VALVE This invention relates to ahydraulic valve and more particularly to a control valve for a powertake-off clutch and brake having means for retaining the valve in theoperating position by the hydraulic pressure of the pressurized fluidfor engaging the clutch.

The conventional power take-off shaft of a tractor is used to driveaccessory equipment such as implements which require power for theiroperation. The power take-off shaft generally extends from the tractorat a point which is convenient for connection to the implement.Generally when the clutch alone is disengaged and no brake is used, acertain amount of rotation is transmitted to the power take-off shaftwhich extends from the tractor.

Although some power take-off shafts are in constant rotation as long asthe engine of the vehicle is in rotation, for safety purposes it isgenerally considered that a disengaging clutch between the drive and thedriven power take-off shafts is desirable. Accordingly, a control valveis used to engage the clutch and another valve may be used to engage thebrake to provide the proper control for the power take-off shaft.Although shields have been provided as safety features to guard againstentangling wearing apparel around the power take-off shaft, it is moredesirable to have an automatic control for braking the power take-offshaft so the danger is eliminated and the power take-off shaft is brakedas soon as the clutch is disengaged.

Accordingly, a power take-off shaft having a hydraulically actuatedclutch and brake can be operated through a single valve tosimultaneously engage the clutch and disengage the brake and vice versawhen the brake is engaged to disengage the clutch. This type of a valveis used with a detent mechanism to hold the actuating lever for thehydraulic control valve in one position or another. There is, howeversome advantage in having this valve control automatic so that once thevehicle engine is stopped and the pump in the hydraulic system no longersupplies pressurized fluid, that the clutch be disengaged. This preventsaccidentally starting the engine with the power take-off engaged andeliminates any drag encountered in rotating the power take-off shaftwhen the vehicle engine is started. Accordingly, this invention providesa control valve without a detent mechanism which can be manuallypositioned to engage the clutch and disengage the brake throughhydraulic means.

Accordingly, it is an object of this invention to provide a controlvalve for a power take-off clutch and brake.

It is another object of this invention to provide a control valve for apower take-off clutch and brake with hydraulic means for retaining thevalve in the clutch engaging position and a spring for returning thevalve to disengage the clutch whenthe engine was stopped and the sourceof pressurized fluid is no longer operatmg.

It is a further object of this invention to provide a control valveoperating a power take-off clutch and brake having manual means tooperate said valve with hydraulic means to retain the clutch engaged andthe brake disengaged, and spring means to disengage the clutch when thefluid in the system is no longer pressurized.

It is a further object of this invention to provide a power take-offclutch and brake control valve with hydraulic means for retaining thevalve in the clutch engaging position and a spring for returning thecontrol valve to a clutch disengaging position when the fluid in thesystem is no longer pressurized.

Accordingly, the objects of this invention are accomplished with a powertake-off shaft driven by the engine through a clutch to a stub shaftextending externally of the tractor. The clutch transmits power to thestub power take-off shaft extending externally of the tractor. A brakeis also positioned for braking the rotation of the stub power take-offshaft once the clutch is disengaged. The clutch and brake arehydraulically actuated. The hydraulic control valve operates to engagethe clutch and disengage the brake simultaneously and vice versa engagethe brake and disengage the clutch when the control valve is manuallyshifted. When the engine of the vehicle is stopped, the source ofpressurized fluid or pump is also stopped and the fluid within thesystem is no longer pressurized. Under these circumstances the brake isalso released and there is no drag on the power take-off shaft when thevehicle engine is started.

Referring to the drawings, the preferred embodiment of this invention isillustrated.

FIG. 1 illustrates a cross section view of the power take-off valve andschematically illustrates the hydraulic system.

FIG. 2 is an end view of the power take-off valve.

FIG. 3 is a cross section view taken on line III-III in FIG. 1.

Referring to the drawings, FIG. 1 illustrates a pump 1 operating from asump 2 to pressurize fluid in the conduit 3. The conduit 3 is connectedto the inlet passage 4. The conduits 5 and 6 are connected to sumppassages in the valve and also are connected through conduit 7 to thesump 2.

Thepump l is .driven by an engine 8 and is continuously in operationwhen the vehicle engine is operated. The passage 4 is connected throughports 90 in sleeve 23 to the high pressure inlet 9 which in turn isconnected to the central bore 10 in the housing 11. The clutch 12 isconnected through the conduit 13 to the clutch actuating passages 160,41 and clutch actuating chamber 18 in the control valve. The accumulatorchamber 30 is connected to the clutch actuating passage 14 throughpassages 61 and 60 and orifice 62. The brake 15 is connected through theconduit 16 to the brake actuating passage and chamber 17. The centralbore 10 is connected to the brake and clutch actuating chambers, as wellas the inlet chamber 9. The sump chamber 14 and chamber 19 are connectedto the sump conduits 5 and 6 respectively, and to the central bore 10.

The inlet passage 4 is in communication with high pressure chamber 9through the pressure limiting valve 22 in the cylindrical opening 20.The cylindrical opening 20 threadedly receives a plug 21 in the righthand end of the housing 11. The pressure limiting valve consists of asleeve 23 having ports in communication with the inlet passage 4 and thechamber 9. The sleeve 23 is biased in the right hand direction by thespring 24 which engages a flange 25 on the sleeve 23 and also engagesradial surface 26 of the cap 27. The force of the spring 24 regulatesthe pressure in the high pressure chamber 9. The spring chamber 28 isconnected to the passage 29 to the sump chamber 14.

The accumulator chamber 30 is formed in the lower part of the housing 11with the plug 31 which is held in position by a snap ring 32. A seal 33is positioned in the annular recess of the plug 31 which engages thehousing 11 to seal the accumulator chamber 30.

The barrel 34 reciprocates in the chamber 30 which in turn receives thesprings 35 and 36 which engage radial surfaces 37 and 38 on the end ofthe plunger 39. The plunger 39 forms a part of the pressure limitingvalve 40 having radial ports 141 to control fluid flow from the clutchactuating chamber 18 to the passage 41. If the pressure in the clutchpassage 18 rises more rapidly than a predetermined rate, it will causethe pressure limiting valve 40 to close off communication between theclutch chamber 18 and the passage 41. The cap 43 threadedly engages theend of the opening formed by the clutch passage 41.

The central bore receives a spool 45. The spool 45 is operated throughpin 47 pivotally connecting manual control lever 46 which is pivotallysupported on the bracket 48 of the housing 11. The spool 45 reciprocateswithin the central bore 10 in response to manual operation of the lever46. A return spring 49 is compressed between the spring retainer 50 andthe radial surface 51 of the barrel 52. The barrel S2 threadedly engagesthe housing 11 and the nut 53 threadedly engages the barrel 52. Thespring retainer 50 is connected to the end of the spool 45 by a snapring 55.

The spool 45 includes the lands 64, 65 and 66 which generally formannular grooves 67 and 68. Throttling orifices 70 and 71 are formed onlands 65 and 66 respectively for throttling fluid flowing to the clutchchamber and retarding flow to sump during initial actuation of theclutch. Orifice passage 101 vents pressurized fluid to sump to limitpressure build-up initially during clutch actuation.

The spool also forms a radial port 74 and an axial passage 75 whichextend to the end of the spool 45 leading into the pressure controlchamber 76. The port 74 and passage 75 permit pressurized fluid to flowinto the chamber 76 when the clutch is actuated biasing the spoolagainst the force of the spring 49 to retain the control valve in theclutch operating position.

The control valve operates in the following manner. The pump 1 receivesfluid from the sump 2 and is driven by the engine 8. The pump 1pressurizes fluid in the conduit 3 which is supplied to the inletpassage 4 to the pressure limiting valve 22. The pressurized fluid flowsthrough the ports 90 into the chamber 9 which surrounds the bore 10.

The lever 46 is used to manually operate the control valve. The controllever 46 can override the operation of the spring 49 on the spool whichnormally biases the spool to a brake actuating position. The controllever 46 is used to operate the valve against the force of the spring 49to actuate the clutch and actuation of the clutch permits thepressurized fluid to flow into the pressure control chamber 76 tomaintain the valve in the open position. The control lever 46 can alsobe operated to position the valve so that neither the brake nor theclutch are engaged.

Spring 49, however, normally returns the piston to the forward positionin which pressurized fluid from the chamber 9 passes through the bore 10to the brake actuating chamber 17. The brake actuating chamber 17 isconnected through the passage 85 and conduit 16 to a hydraulic fluidpressurizing chamber in the brake 15 for normally actuating the brake.in this position the clutch actuating chamber 18, which is incommunication with the hydraulic actuator in the clutch 12 throughconduit 13, is connected to the sump chamber 14 and passage 29. The sumpchamber 14 and passage 29 are connected to spring chamber 28 and returnconduits 5 and 7 to the sump 2. In the brake actuating position there issump pressure in the control chamber 76 and the springs overcome anyfluid forces in the chamber 76 and maintain the valve in the position todisconnect the clutch and engage the brake.

When it is desired to engage the clutch and disengage the brake, thecontrol lever 46 moves in a clockwise direction. This moves the spool 45in a right hand direction with annular groove 67 opening the sumpchamber 19 which is connected through the sump conduits 5 and 7 to sump2 to the brake actuating chamber 17.

This relieves the pressure in the hydraulic actuator of the brake 15,and also closes communication between the high pressure inlet chamber 9and the brake chamber 17 As the control lever 46 continues to move in aclockwise direction, the spool 45 continues to move in a right handdirection. The throttling groove permits restricted flow from the inletchamber 9 to the clutch actuating chamber 18 when the orifice passage101 and throttling groove 71 vent a portion of the pressurized fluid tothe sump chamber 14. The pressure increases in the clutch actuatingchamber 18 and if the opening between the inlet chamber 9 and the clutchactuating chamber 18 is too rapid, the pressure limiting valve 40operates. The operation of the pressure limiting valve 40 is in responseto pressurized fluid in chamber 41 biasing thesleeve 39 against theforce of the springs 35 and 36. This closes the ports 141 in sleeve 39and momentarily retards the pressure build-up in the hydraulic actuatorof clutch 12. Pressure in passage 41 builds up as fluid flows throughpassage 60, orifice 62, passage 61 to the accumulator chamber 30 againstthe force of springs 35 and 36. Normally, the pressure build-up in theclutch 12 is gradual and as the spool 45 moves in the right handdirection the throttling groove 70 moves beyond the edge of the inletchamber 9 permitting more rapid flow to the clutch actuating chamber 18.As the spool 45 continues to move in a right hand direction, the orificepassage 101 moves beyond the sump chamber 14 and into the bore andcloses communication between axial passage and sump chamber 14. In thisposition the clutch 12 is actuated and the pressurized fluid flows intothe pressure control chamber 76 to maintain the clutch in the actuatedposition.

The cross port 74 in the spool 45 connects with axial passage 75 toprovide communication with the hydraulic control chamber 76. With thecommunication between the high pressure chamber 9, clutch chamber 18 andthe control chamber 76, the force of the pressurized fluid in chamber 76biases the spool all the way to the right compressing the spring 49. Solong as the control lever is not manually operated to overcome the forceof fluid pressure in control chamber 76 and the pressure in the highpressure inlet 9 is maintained, the control valve will remain in thisposition. Accordingly, the clutch is engaged and the power take-offshaft delivers the power to the output of the power take-off assembly.

When the engine 8 is stopped the pump 1 is also stopped and there is nolonger pressure in the conduit 3 or the inlet chamber 9. With thedecrease in the pressure in the inlet chamber 9, clutch chamber 18, andcorrespondingly the control chamber 76, the spring 49 biases the spool45 of the control valve to a left hand position. This in turn closes offcommunication between the inlet chamber 9 and the clutch chamber 18 andprovides communication between the inlet chamber 9 and the brake chamber17. With no pressure in the line, however, neither the brake nor theclutch are actuated, and the control valve remains in this position.

When the engine is started and the pump begins, pressurized fluid flowsinto the inlet chamber 9 and the brake is again actuated.

Accordingly, the control valve does not use a mechanical detent tomaintain the spool in a position for engaging the clutch and disengagingthe brake. Any change in position once the clutch is actuated must beprovided through the control lever 46 unless the pump pressure isdecreased to a point that the spring 49 overcomes the pressure of thefluid in chamber 76. Then the shifting of the control valve to actuatethe brake and disengage the clutch is automatic. It can be seen thatafter starting the engine there is no danger of a live power take-offshaft to the operator because the brake is automatically operated unlessthe operator specifically operates the control lever 46 to engage theclutch and disengage the brake.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows: 4

l. A power take-off control valve comprising a valve housing defining abore connected to an inlet passage adapted for connection to a pump, asump passage adapted for connection to a sump, a clutch passage adaptedfor connection to a power take-off clutch, and a brake passage adaptedfor connection to a power take-off brake, a valve element received insaid bore, a spring biasing said valve element to a position connectingthe inlet passage to said brake passage and connecting said clutchpassage to said sump passage, said housing and said valve elementdefining a pressure control chamber in the end of said bore, meansdefining a pressure control passage selectively in communication withsaid clutch passage and said control chamber for receiving pressurizedfluid from said inlet passage for to said control valve.

3. A power tal e-off control valve as set forth "1 claim 1 including apressure limiting valve in said clutch passage to limit the pressure ofpressurized fluid supplied through said clutch passage.

4. A power take-off control valve as set forth in claim 1 including aspring received in said pressure control chamber of said control valvefor biasing said control valve element to a position for disconnectingsaid clutch passage and connecting said brake passage with said inletpassage.

5. A power take-off control valve as set forth in claim 1 wherein saidcontrol element defines a spool, said spool defines a radial passage andan axial passage to provide communication between said clutch passageand said pressure control chamber when said clutch passage receivespressurized fluid from said inlet passage.

6. A power take-off control valve as set forth in claim 1 wherein saidcontrol valve element defines a spool, means defining lands and grooveson said spool, a cross passage in one of said grooves, an axial passageconnecting said cross passage and extending to the end of said spool toprovide communication from said pressure control chamber to said clutchpassage.

7. A power take-off control valve as set forth in claim 1 wherein saidcontrol valve element defines a spool, a control lever pivotallysupported on said housing and pivotally connected to said spool toprovide manual actuating means for said control valve.

8. A power take-off control valve as set forth in claim 1 wherein saidvalve element defines an orifice comm unicating between said clutchpassage and said sump to vent pressurized fluid from said clutch passageto sump during initial connecting between said inlet passage and saidclutch passage.

9. A power take-off control valve as set forth in claim 1 wherein saidspool defines throttling groove for throttling fluid during initialconnection between the inlet passage and the clutch passage.

10. A power take-off control valve as set forth in claim 1 wherein saidvalve housingand said valve element define a pressure control chamber,passage means selectively connectingsaid clutch passage with saidpressure control chamber when said inlet passage is connected to saidclutch passage.

I i k k

1. A power take-off control valve comprising a valve housing defining abore connected to an inlet passage adapted for connection to a pump, asump passage adapted for connection to a sumP, a clutch passage adaptedfor connection to a power take-off clutch, and a brake passage adaptedfor connection to a power take-off brake, a valve element received insaid bore, a spring biasing said valve element to a position connectingthe inlet passage to said brake passage and connecting said clutchpassage to said sump passage, said housing and said valve elementdefining a pressure control chamber in the end of said bore, meansdefining a pressure control passage selectively in communication withsaid clutch passage and said control chamber for receiving pressurizedfluid from said inlet passage for biasing said valve element to aposition providing communication between the clutch passage and theinlet passage and connecting the brake passage to the sump passage andthereby retaining said valve element in this position until pressure isreleased in said clutch passage.
 2. A power take-off control valve asset forth in claim 1 including a pressure limiting valve in said inletpassage means for limiting the inlet pressure provided to said controlvalve.
 3. A power take-off control valve as set forth in claim 1including a pressure limiting valve in said clutch passage to limit thepressure of pressurized fluid supplied through said clutch passage.
 4. Apower take-off control valve as set forth in claim 1 including a springreceived in said pressure control chamber of said control valve forbiasing said control valve element to a position for disconnecting saidclutch passage and connecting said brake passage with said inletpassage.
 5. A power take-off control valve as set forth in claim 1wherein said control element defines a spool, said spool defines aradial passage and an axial passage to provide communication betweensaid clutch passage and said pressure control chamber when said clutchpassage receives pressurized fluid from said inlet passage.
 6. A powertake-off control valve as set forth in claim 1 wherein said controlvalve element defines a spool, means defining lands and grooves on saidspool, a cross passage in one of said grooves, an axial passageconnecting said cross passage and extending to the end of said spool toprovide communication from said pressure control chamber to said clutchpassage.
 7. A power take-off control valve as set forth in claim 1wherein said control valve element defines a spool, a control leverpivotally supported on said housing and pivotally connected to saidspool to provide manual actuating means for said control valve.
 8. Apower take-off control valve as set forth in claim 1 wherein said valveelement defines an orifice communicating between said clutch passage andsaid sump to vent pressurized fluid from said clutch passage to sumpduring initial connecting between said inlet passage and said clutchpassage.
 9. A power take-off control valve as set forth in claim 1wherein said spool defines throttling groove for throttling fluid duringinitial connection between the inlet passage and the clutch passage. 10.A power take-off control valve as set forth in claim 1 wherein saidvalve housing and said valve element define a pressure control chamber,passage means selectively connecting said clutch passage with saidpressure control chamber when said inlet passage is connected to saidclutch passage.